I have to ssh to a remote machine in Europe from Asia every day for my work. But Putty freezes sometimes at totally random times and I have no choice but to close and re-open a new ssh session. It's frustrating especially when I'm editing something or executing a long running program.

I know the question really doesn't have much details ('cause nothing seems to be wrong with the network at all). Has anyone experienced this sort of issue with Putty and had resolved it?

Thanks for your time!

6 Answers 6


The freezing might be a timeout problem. Unfortunatly there seems to be no easy way to fix that, this is all I found on it: Putty FAQ

If this helps that's well and good. But if you want to minimize problems with disconnects you should really start using screen The Persistence feature described below should be particularly interesting.

From wikipedia:

GNU Screen can be thought of as a text version of graphical window managers, or as a way of putting virtual terminals into any login session. It is a wrapper that allows multiple text programs to run at the same time, and provides features that allow the user to use the programs within a single interface productively.

Similar to VNC, GNU Screen allows the user to start applications from one computer, and then reconnect from a different computer and continue using the same application without having to restart it. This makes migration between locations like work and home simple. Screen provides terminal-agnostic functionality so that users can disconnect and reconnect using different terminal types, allowing applications to continue running without being aware of the change in terminals.

Multiple windows
Multiple terminal sessions can be created, each of which usually runs a single application. The windows are numbered, and the user can use the keyboard to switch between them. Some GUI terminal emulators provide tabs or otherwise similar functionality to this. Each window has its own scroll-back buffer, so that output is captured even when the window isn't actively displayed, and that history can be saved even when migrating to another computer. Windows can be split-screened. While some text applications have this functionality built in, Screen allows any application to be split-screened alongside any number of other applications.

Session Sharing
Screen allows multiple computers to connect to the same session at once, allowing collaboration between multiple users. The same computer can also be used to make multiple simultaneous connections, providing alternative functionality to screen-splitting, particularly for computers with multiple monitors.


The easiest solution I've found is to press ctrl-q which resumes the flow control.

Normally you press ctrl-s for saving, which I find highly annoying in putty, I thought it was freezing up at first, but it's actually turning off flow control, ctrl-q turns it back on again.

  • Thank you. This solved my problem. It was driving me crazy!
    – Sam
    Commented Sep 17, 2015 at 12:17

You can have Putty send keep-alive type packets every so often by following the tutorial at http://breakablelinux.blogspot.com/2007/12/preventing-putty-timeouts.html

If the first poster is correct, you can increase the timeout with the following registry edit which should mean less disconnects.

Windows Registry Editor Version 5.00


If you believe that the issue is putty, try another SSH client such as poderosa

  • You can change MTU on router if you using NAT, or change MTU on server. Commented Jan 24, 2020 at 11:41

The only workaround I have found that really works is using a linux vm on my windows machine. I boot that (it's linux mint), and fire up a terminal, and voila, my ssh connection works perfectly, no more freezing issues! I also have found that's the only way to reliably do sshfs.


In my case problem was in large MTU size. You can change MTU on router if you using NAT, but I change MTU on server:

sudo /sbin/ifconfig eth0 mtu 1036
sudo /etc/init.d/networking restart

Ran into this just a few days ago after replacing a network switch. Previous Unifi US-8 had jumbo frames enabled. Replacement Unifi USW-Lite-16-PoE did not have jumbo frames enabled. Symptom was putty ssh sessions would connect and stay connected, UNTIL you scrolled "a lot". It would hang solid. The program was still working, it's just the connection that locked up. Enabling jumbo frames on the switch solved it. Note, the sending device (a windows 10 desktop) and the receiving host (linux) were both configured to use jumbo frames as well.

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